{"id":"UBUNTU-CVE-2016-4020","details":"The patch_instruction function in hw/i386/kvmvapic.c in QEMU does not initialize the imm32 variable, which allows local guest OS administrators to obtain sensitive information from host stack memory by accessing the Task Priority Register (TPR).","modified":"2026-01-30T01:41:49.527276Z","published":"2016-04-14T00:00:00Z","related":["USN-2974-1"],"upstream":["CVE-2016-4020"],"references":[{"type":"REPORT","url":"https://ubuntu.com/security/CVE-2016-4020"},{"type":"REPORT","url":"https://lists.gnu.org/archive/html/qemu-devel/2016-04/msg01118.html"},{"type":"REPORT","url":"http://www.openwall.com/lists/oss-security/2016/04/13/6"},{"type":"ADVISORY","url":"https://ubuntu.com/security/notices/USN-2974-1"},{"type":"REPORT","url":"https://www.cve.org/CVERecord?id=CVE-2016-4020"}],"affected":[{"package":{"name":"qemu","ecosystem":"Ubuntu:14.04:LTS","purl":"pkg:deb/ubuntu/qemu@2.0.0+dfsg-2ubuntu1.24?arch=source&distro=trusty"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"2.0.0+dfsg-2ubuntu1.24"}]}],"versions":["1.5.0+dfsg-3ubuntu5","1.5.0+dfsg-3ubuntu6","1.6.0+dfsg-2ubuntu1","1.6.0+dfsg-2ubuntu2","1.6.0+dfsg-2ubuntu3","1.6.0+dfsg-2ubuntu4","1.7.0+dfsg-2ubuntu1","1.7.0+dfsg-2ubuntu2","1.7.0+dfsg-2ubuntu3","1.7.0+dfsg-2ubuntu4","1.7.0+dfsg-2ubuntu5","1.7.0+dfsg-2ubuntu7","1.7.0+dfsg-2ubuntu8","1.7.0+dfsg-2ubuntu9","1.7.0+dfsg-3ubuntu1~ppa1","1.7.0+dfsg-3ubuntu1","1.7.0+dfsg-3ubuntu2","1.7.0+dfsg-3ubuntu3","1.7.0+dfsg-3ubuntu4","1.7.0+dfsg-3ubuntu5","1.7.0+dfsg-3ubuntu6","1.7.0+dfsg-3ubuntu7","2.0.0~rc1+dfsg-0ubuntu1","2.0.0~rc1+dfsg-0ubuntu2","2.0.0~rc1+dfsg-0ubuntu3","2.0.0~rc1+dfsg-0ubuntu3.1","2.0.0+dfsg-2ubuntu1","2.0.0+dfsg-2ubuntu1.1","2.0.0+dfsg-2ubuntu1.2","2.0.0+dfsg-2ubuntu1.3","2.0.0+dfsg-2ubuntu1.5","2.0.0+dfsg-2ubuntu1.6","2.0.0+dfsg-2ubuntu1.7","2.0.0+dfsg-2ubuntu1.8","2.0.0+dfsg-2ubuntu1.9","2.0.0+dfsg-2ubuntu1.10","2.0.0+dfsg-2ubuntu1.11","2.0.0+dfsg-2ubuntu1.13","2.0.0+dfsg-2ubuntu1.14","2.0.0+dfsg-2ubuntu1.15","2.0.0+dfsg-2ubuntu1.16","2.0.0+dfsg-2ubuntu1.17","2.0.0+dfsg-2ubuntu1.18","2.0.0+dfsg-2ubuntu1.19","2.0.0+dfsg-2ubuntu1.20","2.0.0+dfsg-2ubuntu1.21","2.0.0+dfsg-2ubuntu1.22"],"ecosystem_specific":{"availability":"No subscription required","binaries":[{"binary_name":"qemu","binary_version":"2.0.0+dfsg-2ubuntu1.24"},{"binary_name":"qemu-common","binary_version":"2.0.0+dfsg-2ubuntu1.24"},{"binary_name":"qemu-guest-agent","binary_version":"2.0.0+dfsg-2ubuntu1.24"},{"binary_name":"qemu-keymaps","binary_version":"2.0.0+dfsg-2ubuntu1.24"},{"binary_name":"qemu-kvm","binary_version":"2.0.0+dfsg-2ubuntu1.24"},{"binary_name":"qemu-system","binary_version":"2.0.0+dfsg-2ubuntu1.24"},{"binary_name":"qemu-system-aarch64","binary_version":"2.0.0+dfsg-2ubuntu1.24"},{"binary_name":"qemu-system-arm","binary_version":"2.0.0+dfsg-2ubuntu1.24"},{"binary_name":"qemu-system-common","binary_version":"2.0.0+dfsg-2ubuntu1.24"},{"binary_name":"qemu-system-mips","binary_version":"2.0.0+dfsg-2ubuntu1.24"},{"binary_name":"qemu-system-misc","binary_version":"2.0.0+dfsg-2ubuntu1.24"},{"binary_name":"qemu-system-ppc","binary_version":"2.0.0+dfsg-2ubuntu1.24"},{"binary_name":"qemu-system-sparc","binary_version":"2.0.0+dfsg-2ubuntu1.24"},{"binary_name":"qemu-system-x86","binary_version":"2.0.0+dfsg-2ubuntu1.24"},{"binary_name":"qemu-user","binary_version":"2.0.0+dfsg-2ubuntu1.24"},{"binary_name":"qemu-user-static","binary_version":"2.0.0+dfsg-2ubuntu1.24"},{"binary_name":"qemu-utils","binary_version":"2.0.0+dfsg-2ubuntu1.24"}]},"database_specific":{"source":"https://github.com/canonical/ubuntu-security-notices/blob/main/osv/cve/2016/UBUNTU-CVE-2016-4020.json"}},{"package":{"name":"qemu","ecosystem":"Ubuntu:16.04:LTS","purl":"pkg:deb/ubuntu/qemu@1:2.5+dfsg-5ubuntu10.1?arch=source&distro=xenial"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"1:2.5+dfsg-5ubuntu10.1"}]}],"versions":["1:2.3+dfsg-5ubuntu9","1:2.3+dfsg-5ubuntu10","1:2.4+dfsg-4ubuntu1","1:2.4+dfsg-4ubuntu2","1:2.4+dfsg-4ubuntu3","1:2.4+dfsg-5ubuntu3","1:2.5+dfsg-1ubuntu2","1:2.5+dfsg-1ubuntu3","1:2.5+dfsg-1ubuntu4","1:2.5+dfsg-1ubuntu5","1:2.5+dfsg-5ubuntu1","1:2.5+dfsg-5ubuntu2","1:2.5+dfsg-5ubuntu4","1:2.5+dfsg-5ubuntu6","1:2.5+dfsg-5ubuntu7","1:2.5+dfsg-5ubuntu10"],"ecosystem_specific":{"availability":"No subscription required","binaries":[{"binary_name":"qemu","binary_version":"1:2.5+dfsg-5ubuntu10.1"},{"binary_name":"qemu-block-extra","binary_version":"1:2.5+dfsg-5ubuntu10.1"},{"binary_name":"qemu-guest-agent","binary_version":"1:2.5+dfsg-5ubuntu10.1"},{"binary_name":"qemu-kvm","binary_version":"1:2.5+dfsg-5ubuntu10.1"},{"binary_name":"qemu-system","binary_version":"1:2.5+dfsg-5ubuntu10.1"},{"binary_name":"qemu-system-aarch64","binary_version":"1:2.5+dfsg-5ubuntu10.1"},{"binary_name":"qemu-system-arm","binary_version":"1:2.5+dfsg-5ubuntu10.1"},{"binary_name":"qemu-system-common","binary_version":"1:2.5+dfsg-5ubuntu10.1"},{"binary_name":"qemu-system-mips","binary_version":"1:2.5+dfsg-5ubuntu10.1"},{"binary_name":"qemu-system-misc","binary_version":"1:2.5+dfsg-5ubuntu10.1"},{"binary_name":"qemu-system-ppc","binary_version":"1:2.5+dfsg-5ubuntu10.1"},{"binary_name":"qemu-system-s390x","binary_version":"1:2.5+dfsg-5ubuntu10.1"},{"binary_name":"qemu-system-sparc","binary_version":"1:2.5+dfsg-5ubuntu10.1"},{"binary_name":"qemu-system-x86","binary_version":"1:2.5+dfsg-5ubuntu10.1"},{"binary_name":"qemu-user","binary_version":"1:2.5+dfsg-5ubuntu10.1"},{"binary_name":"qemu-user-binfmt","binary_version":"1:2.5+dfsg-5ubuntu10.1"},{"binary_name":"qemu-user-static","binary_version":"1:2.5+dfsg-5ubuntu10.1"},{"binary_name":"qemu-utils","binary_version":"1:2.5+dfsg-5ubuntu10.1"}]},"database_specific":{"source":"https://github.com/canonical/ubuntu-security-notices/blob/main/osv/cve/2016/UBUNTU-CVE-2016-4020.json"}}],"schema_version":"1.7.3","severity":[{"type":"CVSS_V3","score":"CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:C/C:H/I:N/A:N"},{"type":"CVSS_V3","score":"CVSS:3.0/AV:L/AC:L/PR:L/UI:N/S:C/C:H/I:N/A:N"},{"type":"Ubuntu","score":"medium"}]}